Method and apparatus for transmitting channel state information in wireless communication system

ABSTRACT

A method of transmitting channel information by a User Equipment (UE) when an uplink sub-frame is used for downlink transmission in a communication system using a dynamic Time Division Duplex (TDD) UpLink-DownLink (UL-DL) configuration is provided. The method includes receiving reconfiguration information for reconfiguration of TDD uplink and downlink from an evolved Node B (eNB), measuring interference in a first sub-frame changed from an uplink sub-frame to a downlink sub-frame by the reconfiguration, and transmitting information on interference measured in only the first sub-frame to the eNB in an uplink sub-frame according to a predetermined timing.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims the benefit under 35 U.S.C. §119(a) of a Koreanpatent application filed on Apr. 3, 2013 in the Korean IntellectualProperty Office and assigned Serial number 10-2013-0036550, a Koreanpatent application filed on May 2, 2013 in the Korean IntellectualProperty Office and assigned Serial number 10-2013-0049184, a Koreanpatent application filed on Jun. 19, 2013 in the Korean IntellectualProperty Office and assigned Serial number 10-2013-0070464, a Koreanpatent application filed on Jul. 25, 2013 in the Korean IntellectualProperty Office and assigned Serial number 10-2013-0088081, and a Koreanpatent application filed on Sep. 27, 2013 in the Korean IntellectualProperty Office and assigned Serial number 10-2013-0115224, the entiredisclosures of each of which is hereby incorporated by reference.

TECHNICAL FIELD

The present disclosure relates to a cellular wireless communicationsystem. More particularly, the present disclosure relates to a methodand an apparatus for transmitting channel information in a cellularwireless communication base station.

BACKGROUND

In recent mobile communication systems, an Orthogonal Frequency DivisionMultiple Access (OFDMA) scheme and a Single Carrier-Frequency DivisionMultiple Access (SC-FDMA) scheme similar to the OFDMA scheme areactively researched as schemes useful for high speed data transmissionin a wireless channel. In the multiple access schemes as describedabove, time-frequency resources for carrying data or control informationare allocated and operated in a manner to prevent overlapping of theresources, to establish the orthogonality between users, so as toidentify data or control information of each user.

In a cellular wireless communication system, it is an important factorto support a scalable bandwidth in order to provide a high speedwireless data service.

For example, a Long Term Evolution (LTE) system can have variousbandwidths, such as 20/15/10/5/3/1.4 MHz. Service providers can selectamong the bandwidths described above to provide a service, and there arevarious User Equipment (UEs), ranging from UEs capable of supporting amaximum of a bandwidth of 20 MHz to UEs capable of supporting only aminimum bandwidth of 1.4 MHz. In addition, an LTE-Advanced (LTE-A)system targeted at providing a service of an IMT-Advanced requirementlevel can provide a broadband service up to a maximum of 100 MHzbandwidth through LTE Carrier Aggregation (CA).

For high speed data transmission, an LTE-A system employs a broader bandthan an LTE system. Since the backward compatibility for LTE UEs is alsoimportant, the LTE UEs should also be capable of accessing the LTE-Asystem to use a service provided by the LTE-A system. To this end, inthe LTE-A system, the entire system band is divided into sub-bands orComponent Carriers (CCs), also referred also to as cells, having abandwidth that can be transmitted or received by an LTE UE.Predetermined CCs are combined and data is then generated andtransmitted through each CC. Accordingly, the transmission/receptionprocess of an LTE system according to the related art can be used foreach CC to support a high speed data transmission of the LTE-A system.Each CC or cell can be classified into a primary cell or a secondarycell according to its use or importance in view of a UE. In view of aUE, there is only one primary cell and the other cells except for theprimary cell correspond to secondary cells. In the LTE-A systemaccording to the related art, an uplink control channel is allowed to betransmitted in only the primary cell while an uplink data channel isallowed to be transmitted in both the primary cell and a secondary cell.

Scheduling information for data transmitted through each CC is notifiedas Downlink Control Information (DCI) to a UE. DCI defines variousformats and applies and operates a DCI format determined according towhether the scheduling information is scheduling information for uplinkdata or scheduling information for downlink data, whether a spatialmultiplexing using multiple antennas is applied, whether the DCI is aDCI for power control, and the like. For example, DCI format #1, whichcorresponds to control information for downlink data to which theMultiple Input Multiple Output (MIMO) antenna is not applied, isconfigured by control information as follows.

Resource allocation type 0/1 flag: this control information notifies ofwhether the resource allocation scheme is type 0 or type 1. Type 0applies a bitmap scheme and allocates resources by the unit of ResourceBlock Groups (RBGs). In an LTE or LTE-A system, a basic unit ofscheduling is a Resource Block (RB) expressed by time and frequencydomain resources and an RBG is configured by a plurality of RBs andserves as a basic unit of scheduling in type 0. Type 1 allows allocationof a particular RB in an RBG.

Resource Block assignment: This control information notifies of an RBallocated to data transmission. An expressed resource is determinedaccording to the system bandwidth and resource allocation scheme.

Modulation and Coding Scheme (MCS): This control information notifies ofa modulation scheme and a coding rate used in data transmission.

HARQ process number: This control information notifies of a processnumber of HARQ.

New data indicator: This control information indicates HARQ initialtransmission or retransmission.

Redundancy version: This control information notifies of a redundancyversion of HARQ.

TPC command for PUCCH: This control information notifies of a powercontrol command for a Physical Uplink Control CHannel (PUCCH) which isan uplink control channel.

The DCI as described above is then transmitted through a PhysicalDownlink Control CHannel (PUDCH) which is a downlink physical controlchannel, after being channel-coded and modulated.

The above information is presented as background information only toassist with an understanding of the present disclosure. No determinationhas been made, and no assertion is made, as to whether any of the abovemight be applicable as prior art with regard to the present disclosure.

SUMMARY

Aspects of the present disclosure are to address at least theabove-mentioned problems and/or disadvantages and to provide at leastthe advantages described below. Accordingly, an aspect of the presentdisclosure is to provide a method and an apparatus for transmittingchannel information necessary for scheduling of downlink data by a picoevolved Node B (eNB) when the pico eNB uses a sub-frame, which is usedas an uplink sub-frame by a macro eNB, for downlink transmission in aTime Division Duplex (TDD) communication system supporting a flexiblesub-frame or dynamic TDD UpLink-DownLink (UL-DL) reconfiguration.

However, in a Time Division Duplex (TDD) communication system, a picoevolved Node B (eNB) may use a sub-frame, which is used as an uplinksub-frame by a macro eNB, for downlink transmission through a flexiblesub-frame or dynamic TDD UL-DL reconfiguration. In this event, the macroeNB can control uplink transmission of a macro User Equipment (UE) inthe uplink sub-frame in order to control interference applied to a UE (apico eNB UE) receiving service from a pico eNB by a UE (a macro eNB UE)receiving service from a macro eNB. The pico eNB may require channelinformation from the pico eNB UE in order to schedule downlink data forthe pico eNB UE in a sub-frame which the macro eNB uses as an uplinksub-frame.

Aspects of the present disclosure have been made to solve the problemsas described above, and an aspect of the present disclosure is toprovide a method and an apparatus for transmitting channel informationnecessary for scheduling of downlink data by a pico eNB when the picoeNB uses a sub-frame, which is used as an uplink sub-frame by a macroeNB, for downlink transmission in a TDD communication system supportinga flexible sub-frame or dynamic TDD UL-DL reconfiguration.

In accordance with an aspect of the present disclosure, a method oftransmitting channel information by a UE in a communication system usinga dynamic Time Division Duplex (TDD) UpLink-DownLink (UL-DL)configuration is provided. The method includes receiving reconfigurationinformation for reconfiguration of TDD uplink and downlink from anevolved Node B (eNB), measuring interference in a first sub-framechanged from an uplink sub-frame to a downlink sub-frame by thereconfiguration, and transmitting information on interference measuredin only the first sub-frame to the eNB in an uplink sub-frame accordingto a predetermined timing.

In accordance with another aspect of the present disclosure, a method ofreceiving channel information by an eNB in a communication system usinga dynamic TDD UL-DL configuration is provided. The method includestransmitting reconfiguration information for reconfiguration of TDDuplink and downlink to a UE, transmitting uplink data schedulinginformation including a request for channel information of the UE to theUE, and receiving information on interference measured in only a firstsub-frame changed from an uplink sub-frame to a downlink sub-frame bythe reconfiguration from the UE in an uplink sub-frame according to apredetermined timing.

In accordance with another aspect of the present disclosure, a UEtransmitting channel information in a communication system using adynamic TDD UL-DL configuration is provided. The UE includes atransmission/reception unit configured to transmit and receive a signalto and from an eNB, and a controller configured to receivereconfiguration information for reconfiguration of TDD uplink anddownlink from the eNB, to measure interference in a first sub-framechanged from an uplink sub-frame to a downlink sub-frame by thereconfiguration, and to transmit information on interference measured inonly the first sub-frame to the eNB in an uplink sub-frame according toa predetermined timing.

In accordance with another aspect of the present disclosure, an eNBrequesting channel information in a communication system using a dynamicTDD UL-DL configuration is provided. The eNB includes atransmission/reception unit configured to transmit and receive a signalto and from a UE, and a controller configured to control to transmitreconfiguration information for reconfiguration of TDD uplink anddownlink to the UE, to transmit uplink data scheduling informationincluding a request for channel information of the UE to the UE, and toreceive information on interference measured in only a first sub-framechanged from an uplink sub-frame to a downlink sub-frame by thereconfiguration from the UE in an uplink sub-frame according to apredetermined timing.

In accordance with another aspect of the present disclosure, when a picoeNB supporting dynamic TDD UL-DL reconfiguration or flexible sub-frameuses an uplink sub-frame in downlink transmission, the pico eNB canrequest a pico eNB UE to transmit downlink channel information, whichthe pico eNB can refer to when scheduling downlink data to the pico eNBUE, and the pico eNB UE can transmit the downlink channel information tothe pico eNB at a predetermined timing.

Other aspects, advantages, and salient features of the disclosure willbecome apparent to those skilled in the art from the following detaileddescription, which, taken in conjunction with the annexed drawings,discloses various embodiments of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of certainembodiments of the present disclosure will be more apparent from thefollowing description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 illustrates an example of operation of sub-frames in a typicalTDD frame according to an embodiment of the present disclosure;

FIG. 2 illustrates another example of operation of sub-frames in atypical TDD frame according to an embodiment of the present disclosure;

FIG. 3 illustrates an example of an operation according to a flexiblesub-frame or dynamic Time Division Duplex (TDD) UpLink-DownLink (UL-DL)reconfiguration in a communication system according to an embodiment ofthe present disclosure;

FIG. 4 illustrates a communication system according to an embodiment ofthe present disclosure;

FIG. 5 illustrates an example of transmission of channel informationthrough dynamic TDD UL-DL reconfiguration in a communication systemaccording to an embodiment of the present disclosure;

FIGS. 6A and 6B are flowcharts illustrating an evolved Node B (eNB)operation sequence and a User Equipment (UE) operation sequence forchannel information transmission through dynamic TDD UL-DLreconfiguration in a communication system according to an embodiment ofthe present disclosure;

FIG. 7 illustrates an example of transmission of channel informationthrough a flexible sub-frame in a communication system according toanother embodiment of the present disclosure;

FIGS. 8A and 8B are flowcharts illustrating an eNB operation and a UEoperation for transmission of channel information through flexiblesub-frames in a communication system according to an embodiment of thepresent disclosure;

FIG. 9 is a block diagram illustrating an eNB apparatus in acommunication system according to an embodiment of the presentdisclosure; and

FIG. 10 is a block diagram illustrating a UE apparatus in acommunication system according to an embodiment of the presentdisclosure.

Throughout the drawings, like reference numerals will be understood torefer to like parts, components, and structures.

DETAILED DESCRIPTION

The following description with reference to the accompanying drawings isprovided to assist in a comprehensive understanding of variousembodiments of the present disclosure as defined by the claims and theirequivalents. It includes various specific details to assist in thatunderstanding, but these are to be regarded as merely exemplary.Accordingly, those of ordinary skill in the art will recognize thatvarious changes and modifications of the various embodiments describedherein can be made without departing from the scope and spirit of thepresent disclosure. In addition, descriptions of well-known functionsand constructions may be omitted for clarity and conciseness.

The terms and words used in the following description and claims are notlimited to the bibliographical meanings, but are merely used by theinventor to enable a clear and consistent understanding of the presentdisclosure. Accordingly, it should be apparent to those skilled in theart that the following description of various embodiments of the presentdisclosure is provided for illustration purposes only and not for thepurpose of limiting the present disclosure as defined by the appendedclaims and their equivalents.

It is to be understood that the singular forms “a,” “an,” and “the”include plural referents unless the context clearly dictates otherwise.Thus, for example, reference to “a component surface” includes referenceto one or more of such surfaces.

The following detailed description of various embodiments of the presentdisclosure is based on a Time Division Duplex (TDD) system as a mainsubject. However, the subject matter of the present disclosure isapplicable to other communication systems having similar technicalbackgrounds and channel formation with small variations without largelydeparting from the scope of the present disclosure, and the variationsmay be made by determination of those skilled in the art to which thepresent disclosure pertains.

In general, a TDD communication system uses a common frequency for thedownlink and the uplink but distinguishes transmission/reception of anuplink signal and a downlink signal in the time domain. The Long TermEvolution (LTE) TDD distinguishes between transmission of an uplinksignal and transmission of a downlink signal for each sub-frame. In theLTE TDD, according to traffic loads of the uplink and the downlink,sub-frames for the uplink and the downlink can be uniformly distributedand operated in the time domain, more sub-frames can be allocated to andoperated in the downlink, or more sub-frames can be allocated to andoperated in the uplink. In the LTE, each sub-frame has a length of 1 msand 10 sub-frames configure one radio frame.

TABLE 1 Uplink-downlink Subframe number configuration 0 1 2 3 4 5 6 7 89 0 D S U U U D S U U U 1 D S U U D D S U U D 2 D S U D D D S U D D 3 DS U U U D D D D D 4 D S U U D D D D D D 5 D S U D D D D D D D 6 D S U UU D S U U D

Table 1 shows a TDD UpLink-DownLink configuration (TDD UL-DLconfiguration) defined in the LTE. In Table 1, “D” indicates a sub-frameconfigured for downlink transmission, “U” indicates a sub-frameconfigured for uplink transmission, and “S” indicates a specialsub-frame configured by a Downlink Pilot Time Slot (DwPTS), a GuardPeriod (GP), and an Uplink Pilot Time Slot (UpPTS). The DwPTS allowsdownlink control information transmission like a typical sub-frame andallows downlink data transmission also when the DwPTS is sufficientlylong according to the configuration state of the special sub-frame. TheGP is an interval for accepting transition from the downlink to theuplink and has a length determined by a network configuration, and thelike. The UpPTS is used for transmission of a Sounding Reference Signal(SRS) necessary for estimating an uplink channel state by a UE ortransmission of a Random Access CHannel (RACH) necessary for randomaccess by a UE.

For example, in the case of TDD UL-DL configuration #6, downlink dataand control information can be transmitted in sub-frames #0, #5, and #9and uplink data and control information can be transmitted in sub-frames#2, #3, #4, #7, and #8. In sub-frames #1 and #6, which correspond tospecial sub-frames, downlink control information can be transmitted,downlink data can be transmitted in some cases, and an SRS and an RACHcan be transmitted in the uplink.

In a TDD system, since transmission of a downlink signal or an uplinksignal is allowed only in a particular time interval, it may benecessary to define specific timing relations between uplink/downlinkphysical channels related to each other, such as a control channel fordata scheduling, a scheduled data channel, and an HARQ ACK/NACK channelcorresponding to the data channel.

In an LTE TDD system, an uplink/downlink timing relation between aPhysical Downlink Shared CHannel (PDSCH), which is a physical channelfor downlink data transmission, and a Physical Uplink Shared CHannel(PUSCH) or a Physical Uplink Control CHannel (PUCCH), which is aphysical channel for transmission of an uplink HARQ ACK/NACKcorresponding to the PDSCH, is as follows.

When receiving a PDSCH transmitted in sub-frame (n-k) from an eNB, a UEtransmits an uplink HARQ ACK/NACK for the PDSCH in uplink sub-frame n.In this event, k indicates an element of a set K, which is defined byTable 2 below.

TABLE 2 UL-DL Config- Subframe n uration 0 1 2 3 4 5 6 7 8 9 0 — — 6 — 4— — 6 — 4 1 — — 7, 6 4 — — — 7, 6 4 — 2 — — 8, 7, 4, — — — — 8, 7, 4, —— 6 6 3 — — 7, 6, 11 6, 5 5, — — — — — 4 4 — — 12, 8, 7, 6, 5, 4, — — —— — — 11 7 5 — — 13, 12, 9, — — — — — — — 8, 7, 5, 4, 11, 6 6 — — 7 7 5— — 7 7 —

Table 3 shows rearrangement of sub-frames in which uplink HARQ ACK/NACKscorresponding to PDSCHs are transmitted when the PDSCHs are transmittedin respective Downlink sub-frames (D) or Special sub-frames (S) n ineach TDD UL-DL configuration based on the definition in Table 2.

TABLE 3 UL-DL Subframe n Configuration 0 1 2 3 4 5 6 7 8 9 0 D S U U U DS U U U 4 6 4 6 1 D S U U D D S U U D 7 6 4 7 6 4 2 D S U D D D S U D D7 6 4 8 7 6 4 8 3 D S U U U D D D D D 4 11 7 6 6 5 5 4 D S U U D D D D DD 12 11 8 7 7 6 5 4 5 D S U D D D D D D D 12 11 9 8 7 6 5 4 13 6 D S U UU D S U U D 7 7 7 7 5

FIG. 1 illustrates an example of operation of sub-frames in a typicalTDD frame according to an embodiment of the present disclosure.

Referring to FIG. 1, Table 3 will be described with reference to FIG. 1.

FIG. 1 shows an example of sub-frames in which uplink HARQ ACK/NACKscorresponding to PDSCHs are transmitted when the PDSCHs are transmittedin respective downlink sub-frames or special sub-frames in TDD UL-DLconfiguration #6 of Table 3 based on the definition in Table 3.

For example, an uplink HARQ ACK/NACK 103 corresponding to a PDSCH 101transmitted in sub-frame #0 of radio frame i by an eNB is transmitted insub-frame #7 of radio frame i by a UE. In this event, Downlink ControlInformation (DCI) including scheduling information on the PDSCH 101 istransmitted through a PDCCH in the same sub-frame as the sub-frame inwhich the PDSCH is transmitted. As another example, an uplink HARQACK/NACK 107 corresponding to a PDSCH 105 transmitted in sub-frame #9 ofradio frame i by an eNB is transmitted in sub-frame #4 of radio frame(i+1) by a UE. In the same manner, DCI including scheduling informationon the PDSCH 105 is transmitted through a PDCCH in the same sub-frame asthe sub-frame in which the PDSCH is transmitted.

In an LTE system, a downlink HARQ employs an asynchronous HARQ scheme inwhich a data retransmission time point is not fixed. When an eNB hasreceived an HARQ NACK fed back from a UE in response to an initiallytransmitted HARQ data, the eNB can freely determine a next HARQ dataretransmission time point through a scheduling operation. For the HARQoperation, the UE buffers HARQ data, which has been determined aserroneous as a result of decoding of received data, and then combinesthe buffered HARQ data with next HARQ retransmission data. In thisevent, in order to maintain the reception buffer capacity of the UE, themaximum number of HARQ processes for each TDD UL-DL configuration isdefined as shown in Table 4 below. One HARQ process is mapped to onesub-frame in the time domain.

TABLE 4 TDD UL/DL Maximum number of HARQ configuration processes 0 4 1 72 10 3 9 4 12 5 15 6 6

Referring to the example shown in FIG. 1, the UE decodes a PDSCH 101transmitted in sub-frame #0 of radio frame i by an eNB, and transmits anHARQ NACK 103 in sub-frame #7 of radio frame i when the UE determinesthat the PDSCH has an error. Upon receiving the HARQ NACK, the eNBconfigures retransmission data for the PDSCH 101 by PDSCH 109 andtransmits the configured PDSCH 109 together with a PDCCH. The exampleillustrated in FIG. 1 shows transmission of the retransmission data insub-frame #1 of radio frame (i+1) by reflecting the point that themaximum number of downlink HARQ processes of TDD DL-UL configuration #6is 6 according to the definition in Table 4 described above. A total ofsix downlink HARQ processes 111, 112, 113, 114, 115, and 116 existbetween the initially transmitted PDSCH 101 and the retransmitted PDSCH109.

In an LTE system, the uplink HARQ employs a synchronous HARQ scheme inwhich a data retransmission time point is fixed, differently from thedownlink HARQ. In other words, the uplink/downlink timing relation of aPUSCH, which is a physical channel for uplink data transmission, aPDCCH, which is a downlink control channel preceding the PUSCH, and aPhysical Hybrid Indicator CHannel (PHICH), which is a physical channelfor transmission of a downlink HARQ ACK/NACK corresponding to the PUSCH,is fixed by the rule as follows.

When receiving a PHICH for transmission of a downlink HARQ ACK/NACK or aPDCCH including uplink scheduling control information transmitted froman eNB in sub-frame n, a UE transmits uplink data corresponding to thecontrol information in sub-frame (n+k) through a PUSCH. In this event, kis defined by Table 5 below.

TABLE 5 TDD UL/DL DL subframe number n Configuration 0 1 2 3 4 5 6 7 8 90 4 6 4 6 1 6 4 6 4 2 4 4 3 4 4 4 4 4 4 5 4 6 7 7 7 7 5

When the UE receives a PHICH carrying a downlink HARQ ACK/NACK from theeNB in sub-frame i, the PHICH corresponds to a PUSCH transmitted insub-frame (i-k) by the UE. In this event, k is defined by Table 6 below.

TABLE 6 TDD UL/DL DL subframe number i Configuration 0 1 2 3 4 5 6 7 8 90 7 4 7 4 1 4 6 4 6 2 6 6 3 6 6 6 4 6 6 5 6 6 6 4 7 4 6

FIG. 2 illustrates another example of operation of sub-frames in atypical TDD frame according to an embodiment of the present disclosure.

Referring to FIG. 2, an example is illustrated of sub-frames in whichuplink PUSCHs corresponding to PDCCHs or PHICHs are transmitted andsub-frames in which PHICHs corresponding to the PUSCHs are transmitted,when the PDCCHs or PHICHs are transmitted in respective downlinksub-frames or special sub-frames in the case of TDD UL-DL configuration#1, based on the definition in Table 5 and Table 6 described above.

For example, an uplink PUSCH 203 corresponding to a PDCCH or PHICH 201transmitted in sub-frame #1 of radio frame i by an eNB is transmitted insub-frame #7 of radio frame i by a UE. The eNB transmits a PHICH 205corresponding to the PUSCH to the UE in sub-frame #1 of radio frame(i+1). As another example, an uplink PUSCH 209 corresponding to a PDCCHor PHICH 207 transmitted in sub-frame #6 of radio frame i by the eNB istransmitted in sub-frame #2 of radio frame i by the UE. The eNBtransmits a PHICH 211 corresponding to the PUSCH to the UE in sub-frame#6 of radio frame (i+1).

In an LTE TDD system, in relation to the PUSCH transmission, downlinktransmission of a PDCCH or PHICH corresponding to the PUSCH is limitedin a particular downlink sub-frame, so as to guarantee a minimumtransmission/reception processing time of an eNB and a UE. For example,in the case of TDD UL-DL configuration #1 in FIG. 2, a PDCCH forscheduling the PUSCH or a PHICH corresponding to the PUSCH is nottransmitted in the downlink in sub-frames #0 and #5.

Generally, in a TDD system, after a TDD UL-DL configuration isdetermined, the number of sub-frames for uplink transmission and thenumber of sub-frames for downlink transmission are determined.Accordingly, it is impossible to actively cope with a case in which aparticular eNB at a particular time point requires a larger datacapacity for the downlink transmission than that for the uplinktransmission.

As a result, instead of changing the TDD UL-DL configuration of theentire system, it is possible to consider a dynamic TDD UL-DLreconfiguration or flexible sub-frame scheme in which a particular eNBcan perform a dynamic change according to the required data capacity ofthe uplink and the downlink.

The dynamic TDD UL-DL reconfiguration refers to a scheme of transmittinganother TDD UL-DL reconfiguration other than a currently configured TDDUL-DL reconfiguration to all UEs or a particular UE within an eNBthrough one method selected from system information, Radio ResourceControl (RRC) signaling, Medium Access Control (MAC) signaling, andPhysical layer (PHY) signaling.

In the flexible sub-frame scheme, in order not to influence a guard timethat should exist between a downlink sub-frame and an uplink sub-frame,a flexible sub-frame may be allocated to another uplink sub-frameconsecutively adjacent on the time axis, to the uplink sub-frame alwaysexisting before the downlink sub-frame. In other words, the particularuplink sub-frame can be used for downlink transmission.

FIG. 3 illustrates an example of an operation according to a flexiblesub-frame or dynamic TDD UL-DL reconfiguration in a communication systemaccording to an embodiment of the present disclosure.

Referring to FIG. 3, reference numerals 301 to 304 correspond to anexample to which dynamic TDD UL-DL reconfiguration is applied, andreference numerals 311 to 313 correspond to an example in which aflexible sub-frame is applied to TDD UL-DL configuration #1.

Referring to reference numerals 301 to 304, one radio frame includes aplurality of sub-frames, 10 sub-frames in the present embodiment,wherein reference numeral 301 corresponds to radio frames having indexesof (n−1) and n and reference numeral 302 corresponds to radio frameshaving indexes of (n+1) and (n+2).

Configuration #3 301 is configured for radio frames having indexes of(n−1) and n as the TDD UL-DL configuration within the eNB. According tothe determination of the eNB based on the required data capacity of theuplink and the downlink, the TDD UL-DL configuration may be reconfiguredinto configuration #4 302 from the radio frame having an index of (n+1).In this event, the reconfiguration information can be transmittedthrough one of system information, higher layer signaling (e.g. RRCsignaling), MAC signaling, and physical layer signaling.

Sub-frame #4, which is an uplink sub-frame 303 in TDD UL-DLconfiguration #3 301, changes into a downlink sub-frame 304 from a radioframe having an index of n according to reconfiguration into TDD UL-DLconfiguration #4. Accordingly, a macro eNB uses sub-frame #4 for uplinktransmission in a state without change in the TDD UL-DL configurationand a pico eNB can use sub-frame #4 for downlink transmission throughTDD UL-DL reconfiguration.

The TDD UL-DL configuration in the eNB is configuration #1 311. When twoflexible sub-frames are operated in one radio frame of TDD UL-DLconfiguration #1, the two flexible sub-frames may be configured bysub-frames 312 and 313. Among the uplink sub-frames, sub-frames 312 and313 adjacent to downlink sub-frames are operated as flexible sub-frames.Sub-frames #3 and #8 may be operated as flexible sub-frames. Each ofsub-frame #3 312 and sub-frame #8 313 described above is marked by UFimplying an Uplink Flexible sub-frame which can be used for downlinktransmission.

According to various embodiments, an eNB can notify a UE of an uplinksub-frame to be operated as a flexible sub-frame, through separateinformation or signaling. Otherwise, without separate information orsignaling from an eNB, a UE may identify an uplink sub-frame operated asa flexible sub-frame by itself. Sub-frames 312 and 313, which are uplinksub-frames in TDD UL-DL configuration #1 311, are configured as flexiblesub-frames and used for downlink transmission by a pico eNB.Accordingly, a macro eNB uses sub-frame #3 for uplink transmission sincethe macro eNB uses TDD UL-DL configuration #1 without change, and a picoeNB can use sub-frame #3 for downlink transmission through flexiblesub-frame configuration.

FIG. 4 illustrates a concept of a communication system according to anembodiment of the present disclosure.

Referring to FIG. 4, a state is illustrated in which a particular eNBuses uplink sub-frame for downlink transmission through a flexiblesub-frame or TDD UL-DL reconfiguration in a TDD system including aplurality of eNBs operating based on the same TDD UL-DL configuration.

Referring to the part indicated by reference numeral 401, when a macroeNB and pico eNBs use a corresponding uplink sub-frame for uplinktransmission without change and adjacently located pico eNBs use thecorresponding uplink sub-frame for downlink transmission through aflexible sub-frame or dynamic TDD UL-DL reconfiguration, pico eNB UEsreceiving the downlink transmission from the adjacently located picoeNBs receive interference from other macro eNB UEs or other pico eNBUEs, which are located adjacent to the pico eNB UEs receiving thedownlink transmission and performing the uplink transmission to themacro eNB and the pico eNBs (see 402 and 403). In FIG. 4, application ofinterference is indicated by arrows named “interference”.

Referring to the part indicated by reference numeral 411, when aparticular pico eNB uses an uplink sub-frame for downlink transmissionthrough a flexible sub-frame or dynamic TDD UL-DL reconfiguration, inorder to enable a pico eNB UE to receive a downlink signal withoutinterference, a macro eNB and pico eNBs may not schedule uplink data inthe uplink sub-frame. Through this scheme, the macro eNB and the picoeNBs can prevent generation of interference to downlink data receptionof a particular pico eNB UE (see 412 and 413).

Through the method described above with reference to FIG. 4, theparticular pico eNB can use an uplink sub-frame for downlinktransmission without interference (from a macro eNB). When the uplinksub-frame is used for downlink transmission, a channel state of theuplink sub-frame is different from a channel state of a typical downlinksub-frame. This is because all eNBs can perform downlink datatransmission in a typical downlink sub-frame.

Accordingly, when a pico eNB uses an uplink sub-frame for downlinktransmission, channel information which the pico eNB can refer to forscheduling of downlink data is necessary. In addition, a scheme fornotifying a pico eNB of channel information by a pico eNB UE may beneeded.

FIG. 5 illustrates an example of transmission of channel informationthrough dynamic TDD UL-DL reconfiguration in a communication systemaccording to an embodiment of the present disclosure.

Referring to FIG. 5, a method is described for allowing a pico eNB UE totransmit downlink channel information which a pico eNB can refer to inscheduling of downlink data, when the pico eNB UE uses a sub-frame,which is used as an uplink sub-frame by a macro eNB, for downlinktransmission through dynamic TDD UL-DL reconfiguration in a TDD system.

In the examples described herein with respect to FIG. 5, it is assumedthat, when a pico eNB uses a sub-frame, used as an uplink sub-frame by amacro eNB, for downlink transmission through dynamic TDD UL-DLreconfiguration, the present disclosure does not allow uplinktransmission in an adjacent macro eNB or pico eNB through interferencecontrol of a macro eNB and other pico eNBs as in FIG. 4 Further, for TDDUL-DL reconfiguration, sub-frame sets for all downlink sub-frames can beclassified according to the TDD UL-DL configurations and thentransmitted in advance as a higher layer signal to a UE. Accordingly, atthe time of TDD UL-DL reconfiguration, all sub-frames used for downlinktransmission belong to one sub-frame among two sub-frame sets (based onan assumption that two sub-frame sets exist).

As a result, the embodiment of the present disclosure described belowprovides a scheme by which, when adjacent pico eNBs using the sub-framefor downlink transmission exist, it is possible to detect channelinformation including downlink interference from the corresponding picoeNBs, i.e. a method in which a pico eNB UE measures channel informationin a corresponding sub-frame and reports measured channel information tothe pico eNB.

The frame structure including the parts indicated by reference numerals501 to 503 is based on a situation in which the TDD UL-DL configurationof a pico eNB is reconfigured from #1 to #2. In each TDD UL-DLconfiguration, sub-frames having the same pattern configure one uplinkHARQ process and sub-frames having no pattern may imply sub-frameshaving no uplink HARQ process.

Referring to reference numeral 503, a macro eNB or particular pico eNBsuse sub-frame #3 for uplink transmission, and the pico eNB according toan embodiment of the present disclosure uses sub-frame #3 for downlinktransmission.

In UL-DL configuration #2 through UL-DL reconfiguration, sub-frame #3 isa sub-frame in which an uplink HARQ process is configured. As a result,in sub-frame #3, an UpLink (UL) grant (or uplink data schedulinginformation) requesting channel information may be transmitted, whereina CQI request field included in the UL grant is turned ON to requestchannel information in the sub-frame. In this event, the UE measures theinterference in only sub-frame #3 at the time of interferencemeasurement for generation of channel information. At the time ofinterference measurement, the UE does not average the interferencetogether with interference in other sub-frames (e.g. sub-frame #3 usedfor uplink transmission after another UL-DL reconfiguration in a nextradio frame, sub-frames belonging to the same sub-frame set, orsub-frames belonging to the same CSI process). This is because thesub-frame in the example described above may be used for uplinktransmission in the next radio frame. When another UL-DL reconfigurationis not performed in the next radio frame (i.e., when the UL-DLconfiguration is maintained), interference may be processed together insub-frame #3 in the next radio frame. In the above description,“averaging” or “being processed together” implies inputting to oneidentical filter calculating the quantity of interference within a UE. AUE may include, in addition to a filter (or filters) for calculating thequantity of interference of a typical downlink sub-frame, a filter forcalculating the quantity of interference in a sub-frame such assub-frame #3 when there is signaling for another UL-DL reconfiguration.

The UE transmits uplink data including channel information in sub-frame#7 based on UL HARQ timing defined in UL-DL configuration #2. In thisevent, uplink data may be configured by only channel information or maybe multiplexed with general data.

Next, the frame structure including the parts indicated by referencenumerals 511 to 513 is based on a situation in which the TDD UL-DLconfiguration of a pico eNB is reconfigured from #1 to #4.

Referring to reference numeral 513, a macro eNB or particular pico eNBsuse sub-frame #4 for uplink transmission, and the pico eNB according toan embodiment of the present disclosure uses sub-frame #4 for downlinktransmission.

In UL-DL configuration #4 through UL-DL reconfiguration, sub-frame #4 isa sub-frame in which an uplink HARQ process does not exist. As a result,a UL grant requesting channel information cannot be transmitted insub-frame #4. A method of requesting channel information from a UE by aneNB in a sub-frame in which a UL grant requesting the channelinformation cannot be transmitted described is described.

First, a method in which an eNB transmits a UL grant requesting channelinformation in sub-frame #4 despite that a UL grant requesting channelinformation cannot be transmitted in sub-frame #4 is proposed. To thisend, the eNB can request the channel information in the sub-frame byturning ON the CQI request field in the UL grant. In this event, the UEmeasures the interference in only sub-frame #4 at the time ofinterference measurement for generation of channel information. At thetime of interference measurement, the UE does not average theinterference together with interference in other sub-frames (e.g.sub-frame #4 used for uplink transmission after another UL-DLreconfiguration in a next radio frame, sub-frames belonging to the samesub-frame set, or sub-frames belonging to the same CSI process). This isbecause the sub-frame in the example described above may be used foruplink transmission in the next radio frame. When another UL-DLreconfiguration is not performed in the next radio frame (i.e., when theUL-DL configuration is maintained), interference can be processedtogether in sub-frame #4 in the next radio frame. In the abovedescription, “averaging” or “being processed together” implies inputtingto one identical filter calculating the quantity of interference withina UE. The UE may be provided with, in addition to a filter (or filters)for calculating the quantity of interference of a typical downlinksub-frame, a filter for calculating the quantity of interference in asub-frame such as sub-frame #4 when there is signaling for another UL-DLreconfiguration.

In response to the request for channel information, uplink dataincluding channel information is transmitted in sub-frame #2, which isthe nearest uplink sub-frame appearing after four sub-frames fromsub-frame #4 described above. In this event, uplink data may beconfigured by only channel information or may be multiplexed withgeneral data.

Since sub-frame #2, which is the nearest uplink sub-frame, configures anuplink HARQ process together with downlink sub-frame #8, a UL grantrequesting channel information can be transmitted in downlink sub-frame#8 also. When the UL grant requesting channel information in sub-frame#4 and the UL grant requesting channel information in downlink sub-frame#8 are simultaneously transmitted, the following UE operations can betaken into consideration.

First, a UE does not expect to simultaneously receive a UL grantrequesting channel information in sub-frame #4 and a UL grant requestingchannel information in sub-frame #8. Accordingly, the UE does notperform any transmission in uplink sub-frame #2. That is, the UE canomit (or disregard) transmission of channel information in uplinksub-frame #2.

Second, the UE first processes a UL grant requesting channel informationin sub-frame #4. Accordingly, the UE transmits channel information ofsub-frame #4 in uplink sub-frame #2.

Third, the UE first processes a UL grant requesting channel informationin sub-frame #8. Accordingly, the UE transmits channel information ofsub-frame #8 in uplink sub-frame #2.

Fourth, the UE processes both the UL grants requesting channelinformation in sub-frame #8 and sub-frame #4 as valid. Accordingly, theUE multiplexes and transmits channel information of sub-frame #8 andsub-frame #4 in uplink sub-frame #2. In the multiplexing, the sub-framesmay be sequentially multiplexed from a sub-frame having a lowestsub-frame index. The UE may first multiplex and transmit channelinformation of sub-frame #4 and then multiplex and transmit channelinformation of sub-frame #8. However, the multiplexing based on thesub-frame indexes is just an embodiment and the present disclosure isnot always limited to this embodiment. For example, the channelinformation may be multiplexed according to predetermined priorities.

Second, a method of transmitting a UL grant requesting channelinformation of sub-frame #4 in sub-frame #8 corresponding to the nearestdownlink sub-frame in which an uplink HARQ process exists aftersub-frame #4 is proposed. To this end, when transmitting the UL grant insub-frame #8, the eNB can indicate multi-cluster transmission in orderto distinguish from channel information for sub-frame #8. In this event,the UE measures the interference in only sub-frame #4 at the time ofinterference measurement for generation of channel information ofsub-frame #4. At the time of interference measurement, the UE does notaverage the interference together with interference in other sub-frames(e.g. sub-frame #4 used for uplink transmission after another UL-DLreconfiguration in a next radio frame, sub-frames belonging to the samesub-frame set, or sub-frames belonging to the same CSI process). This isbecause the sub-frame in the example described above may be used foruplink transmission in the next radio frame. When another UL-DLreconfiguration is not performed in the next radio frame, that is, whenthe UL-DL configuration is maintained, interference can be processedtogether in sub-frame #4 in the next radio frame. In the abovedescription, “averaging” or “being processed together” implies inputtingto one identical filter calculating the quantity of interference withina UE. The UE may be provided with, in addition to a filter (or filters)for calculating the quantity of interference of a typical downlinksub-frame, a filter for calculating the quantity of interference in asub-frame such as sub-frame #4 when there is signaling for another UL-DLreconfiguration.

The UE transmits uplink data including channel information throughmulti-cluster in sub-frame #2 of the next radio frame based on UL HARQtiming defined in UL-DL configuration #2. The transmission throughmulti-cluster implies that one cluster among two transmissible clusterscan be used for transmission of channel information of sub-frame #3. Inthis event, uplink data may be configured by only channel information ormay be multiplexed with general data.

Third, a method in which an eNB transmits a UL grant requesting channelinformation in sub-frame #4 even though a UL grant requesting channelinformation cannot be transmitted in sub-frame #4 is proposed. To thisend, the eNB requests the channel information in the sub-frame byturning ON the CQI request field in the UL grant, which is the same asin the first method described above. However, the present method isdifferent from the first method in that, at the time of transmission ofchannel information by a UE in response to a request for the channelinformation from an eNB, uplink data including channel information istransmitted in a universal uplink sub-frame (sub-frame #2) alwaysconfigured as an uplink sub-frame in all UL-DL configurations. The UEmeasures the interference in only sub-frame #4 at the time ofinterference measurement for generation of channel information. At thetime of interference measurement, the UE does not average theinterference together with interference in other sub-frames (e.g.sub-frame #4 used for uplink transmission after another UL-DLreconfiguration in a next radio frame, sub-frames belonging to the samesub-frame set, or sub-frames belonging to the same CSI process). This isbecause the sub-frame in the example described above may be used foruplink transmission in the next radio frame. When another UL-DLreconfiguration is not performed in the next radio frame (i.e., when theUL-DL configuration is maintained), interference can be processedtogether in sub-frame #4 in the next radio frame. In the abovedescription, “averaging” or “being processed together” implies inputtingto one identical filter calculating the quantity of interference withina UE. The UE may be provided with, in addition to a filter (or filters)for calculating the quantity of interference of a typical downlinksub-frame, a filter for calculating the quantity of interference in asub-frame such as sub-frame #4 when there is signaling for another UL-DLreconfiguration.

In this event, uplink data may be configured by only channel informationor may be multiplexed with general data.

Fourth, a method in which an eNB transmits a UL grant requesting channelinformation in sub-frame #4 despite that a UL grant requesting channelinformation cannot be transmitted in sub-frame #4 is proposed. To thisend, the eNB requests the channel information in the sub-frame byturning ON the CQI request field in the UL grant, which is the same asin the first and third methods described above. However, in the presentembodiment, transmission of channel information of a UE in response to arequest for the channel information from an eNB is performed accordingto DL HARQ timing defined in UL-DL configuration #4 through UL-DLreconfiguration (i.e., timing defined based on PUCCH transmission timingfor a PDCCH (or PDSCH)). PDCCH (or PDSCH) transmission timing is usedfor transmission of a UL grant requesting channel information, and PUCCHtransmission timing is used for transmission of a PUSCH by the UL grantrequesting the channel information.

Accordingly, when a UL grant requesting channel information istransmitted in sub-frame #4, uplink data including channel informationis transmitted in uplink sub-frame #2 according to DL HARQ timingdefined in sub-frame #4 of UL-DL configuration #4, which is differentfrom the first and third methods. In this event, uplink data may beconfigured by only channel information or may be multiplexed withgeneral data. The UE measures the interference in only sub-frame #4 atthe time of interference measurement for generation of the channelinformation.

At the time of interference measurement, the UE does not average theinterference together with interference in other sub-frames (e.g.sub-frame #4 used for uplink transmission after another UL-DLreconfiguration in a next radio frame, sub-frames belonging to the samesub-frame set, or sub-frames belonging to the same CSI process). This isbecause the sub-frame in the example described above may be used foruplink transmission in the next radio frame. When another UL-DLreconfiguration is not performed in the next radio frame, that is, whenthe UL-DL configuration is maintained, interference can be processedtogether in sub-frame #4 in the next radio frame. In the abovedescription, “averaging” or “being processed together” implies inputtingto one identical filter calculating the quantity of interference withina UE. The UE may be provided with, in addition to a filter (or filters)for calculating the quantity of interference of a typical downlinksub-frame, a filter for calculating the quantity of interference in asub-frame such as sub-frame #4 when there is signaling for another UL-DLreconfiguration.

FIGS. 6A and 6B are flowcharts illustrating an eNB operation sequenceand a UE operation sequence, respectively, for channel informationtransmission through dynamic TDD UL-DL reconfiguration in acommunication system according to an embodiment of the presentdisclosure.

Referring to FIG. 6A, in operation 601, an eNB transmits a new TDD UL-DLconfiguration to a UE in order to change a current TDD UL-DLconfiguration. The reconfiguration information for the TDD UL-DLconfiguration can be transmitted to the UE through one of systeminformation, RRC signaling, MAC signaling, and PHY signaling.

In operation 602, the eNB determines whether a UL HARQ process exists insub-frame n, which was an uplink sub-frame before reconfiguration and ischanged to a downlink sub-frame after the reconfiguration. Whensub-frame n is a sub-frame in which a mapped UL HARQ process exists, theeNB transmits a UL grant requesting channel information (or uplink datascheduling information) to the UE in sub-frame n in operation 603. Tothis end, the eNB can request the channel information in the sub-frameby turning ON the CQI request field included in the UL grant, asdescribed above.

In operation 604, the eNB receives channel information of the sub-framen in an uplink sub-frame according to UL HARQ timing defined in the newUL-DL configuration.

As a result of the determination in operation 602, when sub-frame n is asub-frame in which a UL HARQ process mapped to sub-frame n does notexist, the eNB transmits a UL grant requesting channel information ofsub-frame n in a sub-frame according to the first, second, or thirdmethod proposed by the present disclosure described above with referenceto FIG. 5 in operation 605.

As described above, the first and third methods include transmitting aUL grant requesting channel information in sub-frame n which does notallow transmission of the UL grant, and the second method includestransmitting a UL grant requesting channel information in the nearestdownlink sub-frame in which a UL HARQ process exists after sub-frame n.

In operation 606, the eNB receives channel information of the sub-framen in a sub-frame according to the first, second, or third methodproposed by the present disclosure as described above with reference toFIG. 5.

As described above, in the first method, the eNB receives the channelinformation in the nearest sub-frame appearing after four sub-framesfrom the sub-frame in which the UL grant has been transmitted. In thesecond method, the eNB receives the channel information based onmulti-cluster according to UL HARQ timing defined for the sub-frame inwhich the UL grant has been transmitted. In the third method, the eNBreceives the channel information in the sub-frame in which the UL granthas been transmitted.

Referring to FIG. 6B, in operation 611, a UE receives a new TDD UL-DLconfiguration from an eNB in order to change a current TDD UL-DLconfiguration. The reconfiguration information for the TDD UL-DLconfiguration can be received from the UE through one of systeminformation, RRC signaling, MAC signaling, and PHY signaling.

In operation 612, the UE determines whether a UL HARQ process exists insub-frame n, which was an uplink sub-frame before reconfiguration and ischanged to a downlink sub-frame after the reconfiguration. Whensub-frame n is a sub-frame in which a mapped UL HARQ process exists, theUE receives a UL grant requesting channel information (or uplink datascheduling information) from the eNB in sub-frame n in operation 613.The UE can determine whether channel information has been requested,based on whether a CQI request field included in the UL grant has beenconfigured to ON. The UE measures the interference in only sub-frame #3at the time of interference measurement for generation of channelinformation, after or before requesting the channel information. At thetime of interference measurement, the UE does not average theinterference together with interference in other sub-frames (e.g.sub-frame #n used for uplink transmission after another UL-DLreconfiguration in a next radio frame, sub-frames belonging to the samesub-frame set, or sub-frames belonging to the same CSI process). This isbecause the sub-frame in the example described above may be used foruplink transmission in the next radio frame.

When another UL-DL reconfiguration is not performed in the next radioframe (i.e., when the UL-DL configuration is maintained), interferencecan be processed together in sub-frame #n in the next radio frame. Inthe above description, “averaging” or “being processed together” impliesinputting to one identical filter calculating the quantity ofinterference within a UE. A UE may include, in addition to a filter (orfilters) for calculating the quantity of interference of a typicaldownlink sub-frame, a filter for calculating the quantity ofinterference in a sub-frame such as sub-frame #n when there is signalingfor another UL-DL reconfiguration.

In operation 614, the UE transmits channel information of the sub-framen in an uplink sub-frame according to UL HARQ timing defined in the newUL-DL configuration.

As a result of the determination in operation 612, when sub-frame n is asub-frame in which a mapped UL HARQ process does not exist, the UEreceives a UL grant requesting channel information of sub-frame n in asub-frame according to the first, second, or third method proposed bythe present disclosure described above with reference to FIG. 5 inoperation 615.

As described above, the first and third methods include receiving a ULgrant requesting channel information in sub-frame n which does not allowtransmission of the UL grant, and the second method includes receiving aUL grant requesting channel information in the nearest downlinksub-frame in which a UL HARQ process exists after sub-frame n.

The UE measures the interference in only sub-frame #3 at the time ofinterference measurement for generation of channel information, after orbefore requesting the channel information. At the time of interferencemeasurement, the UE does not average the interference together withinterference in other sub-frames (e.g. sub-frame #n used for uplinktransmission after another UL-DL reconfiguration in a next radio frame,sub-frames belonging to the same sub-frame set, or sub-frames belongingto the same CSI process). This is because the sub-frame in the exampledescribed above may be used for uplink transmission in the next radioframe. When another UL-DL reconfiguration is not performed in the nextradio frame (i.e., when the UL-DL configuration is maintained),interference can be processed together in sub-frame #n in the next radioframe. In the above description, “averaging” or “being processedtogether” implies inputting to one identical filter calculating thequantity of interference within a UE. A UE may include, in addition to afilter (or filters) for calculating the quantity of interference of atypical downlink sub-frame, a filter for calculating the quantity ofinterference in a sub-frame such as sub-frame #n when there is signalingfor another UL-DL reconfiguration.

In operation 616, the UE transmits channel information of sub-frame n ina sub-frame according to the first, second, or third method proposed bythe present disclosure as described above with reference to FIG. 5.

As described above, in the first method, the UE transmits the channelinformation in the nearest sub-frame appearing after four sub-framesfrom the sub-frame in which the UL grant has been transmitted. In thesecond method, the UE transmits the channel information based onmulti-cluster according to UL HARQ timing defined for the sub-frame inwhich the UL grant has been transmitted. In the third method, the UEtransmits the channel information in the sub-frame in which the UL granthas been transmitted.

FIG. 7 illustrates an example of transmission of channel informationthrough a flexible sub-frame in a communication system according toanother embodiment of the present disclosure.

Referring to FIG. 7, a method is illustrated for allowing a pico eNB UEto transmit downlink channel information which a pico eNB can refer toin scheduling of downlink data, when the pico eNB UE uses a sub-frame,which is used as an uplink sub-frame by a macro eNB, for downlinktransmission through a flexible sub-frame in a TDD system.

In the example given in FIG. 7, it is assumed that, when a pico eNB usesa sub-frame, used as an uplink sub-frame by a macro eNB, for downlinktransmission through a flexible sub-frame, the present disclosure doesnot allow uplink transmission in an adjacent macro eNB or pico eNBthrough interference control of a macro eNB and other pico eNBs as inFIG. 4. Accordingly, a scheme for obtaining channel informationincluding downlink interference from adjacent pico eNBs using thesub-frame for downlink transmission is provided.

The sub-frames indicated by reference numerals 702 to 705 is based on asituation in which the TDD UL-DL configuration of the pico eNB isconfiguration #1 and sub-frames #3 and #8 are operated as flexiblesub-frames. In TDD UL-DL configuration #1 701, sub-frames having thesame pattern configure one uplink HARQ process and sub-frames having nopattern correspond to sub-frames having no uplink HARQ process.

A macro eNB or particular pico eNBs use sub-frames #3 and #8 for uplinktransmission, and the pico eNB uses sub-frames #3 and #8 for downlinktransmission. In a method proposed by the present disclosure fortransmission of channel information, if a pico eNB uses sub-frames #3702 and #8 703 of radio frame n for downlink data transmission,sub-frames #3 704 and #8 705 of the next radio frame, i.e. radio frame(n+1), are used for uplink data transmission.

Downlink sub-frame #9, which originally configures one UL HARQ processtogether with uplink sub-frame #3 702 in TDD UL-DL configuration #1 701,no longer configures one UL HARQ process together with uplink sub-frame#3 as sub-frame #3 702 is used for downlink data transmission.Accordingly, if a UL grant requesting channel information is transmittedin sub-frame #3 702 of radio frame n, the UE transmits uplink dataincluding the channel information in sub-frame #3 704 of the next radioframe, i.e. radio frame (n+1). The UE measures the interference in onlysub-frame #3 of radio frame n at the time of interference measurementfor generation of the channel information. At the time of interferencemeasurement, the UE does not average the interference together withinterference in other sub-frames (e.g. sub-frame #3 used for uplinktransmission after another UL-DL reconfiguration in a next radio frame,sub-frames belonging to the same sub-frame set, or sub-frames belongingto the same CSI process). This is because the sub-frame in the exampledescribed above may be used for uplink transmission in the next radioframe. When another UL-DL reconfiguration is not performed in the nextradio frame (i.e., when the UL-DL configuration is maintained),interference may be processed together in sub-frame #3 in the next radioframe. In the above description, “averaging” or “being processedtogether” implies inputting to one identical filter calculating thequantity of interference within a UE. A UE may include, in addition to afilter (or filters) for calculating the quantity of interference of atypical downlink sub-frame, a filter for calculating the quantity ofinterference in a sub-frame such as sub-frame #3 when there is signalingfor another UL-DL reconfiguration.

Similarly, downlink sub-frame #4, which originally configures one ULHARQ process together with uplink sub-frame #8 703 in TDD UL-DLconfiguration #1 701, no longer configures one UL HARQ process togetherwith uplink sub-frame #8 as sub-frame #8 703 is used for downlink datatransmission. Accordingly, if a UL grant requesting channel informationis transmitted in sub-frame #8 703 of radio frame n, the UE transmitsuplink data including the channel information in sub-frame #8 705 of thenext radio frame, i.e. radio frame (n+1). The UE measures theinterference in only sub-frame #8 of radio frame n at the time ofinterference measurement for generation of the channel information. Atthe time of interference measurement, the UE does not average theinterference together with interference in other sub-frames (e.g.sub-frame #8 used for uplink transmission after another UL-DLreconfiguration in a next radio frame, sub-frames belonging to the samesub-frame set, or sub-frames belonging to the same CSI process). This isbecause the sub-frame in the example described above may be used foruplink transmission in the next radio frame. When another UL-DLreconfiguration is not performed in the next radio frame (i.e., when theUL-DL configuration is maintained), interference can be processedtogether in sub-frame #8 in the next radio frame. In the abovedescription, “averaging” or “being processed together” implies inputtingto one identical filter calculating the quantity of interference withina UE. A UE may include, in addition to a filter (or filters) forcalculating the quantity of interference of a typical downlinksub-frame, a filter for calculating the quantity of interference in asub-frame such as sub-frame #8 when there is signaling for another UL-DLreconfiguration.

In this event, the uplink data may be configured by only channelinformation or may be multiplexed with general data. Through the methoddescribed above, an uplink sub-frame can be used for downlink datatransmission through a flexible sub-frame configuration in sub-frames ofone radio frame for every two radio frames.

FIGS. 8A and 8B are flowcharts illustrating an eNB operation and a UEoperation, respectively, for transmission of channel information throughflexible sub-frames in a communication system according to an embodimentof the present disclosure.

Referring to FIG. 8A, in operation 801, an eNB transmits relatedinformation to a UE in order to use a UL flexible sub-frame of a currentTDD UL-DL configuration in downlink transmission. The information on theflexible sub-frame can be transmitted to the UE through one of systeminformation, RRC signaling, MAC signaling, and physical layer signaling.

In operation 802, the eNB determines whether flexible sub-frame n isused for downlink transmission. When flexible sub-frame n is used fordownlink transmission, the eNB transmits a UL grant requesting channelinformation to the UE in sub-frame n according to the method describedabove with reference to FIG. 7 in operation 803.

Further, in operation 804, the eNB receives channel information ofsub-frame n of a previous radio frame from the UE in sub-frame n of aradio frame having a next index according to the method disclosuredescribed above with reference to FIG. 7.

As a result of the determination in operation 802, if flexible sub-framen is used for uplink transmission without change, it is unnecessary totransmit downlink channel information for flexible sub-frame n to theUE.

Referring to FIG. 8B, in operation 811, a UE receives relatedinformation from an eNB in order to use a UL flexible sub-frame of acurrent TDD UL-DL configuration in downlink transmission. Theinformation on the flexible sub-frame can be received from the eNBthrough one of system information, RRC signaling, MAC signaling, andphysical layer signaling.

In operation 812, the UE determines whether flexible sub-frame n is usedfor downlink transmission. When flexible sub-frame n is used fordownlink transmission, the UE receives a UL grant requesting channelinformation from the eNB in sub-frame n according to the method proposedby the present disclosure described above with reference to FIG. 7 inoperation 813.

The UE measures the interference in only sub-frame #3 at the time ofinterference measurement for generation of channel information, after orbefore requesting the channel information. At the time of interferencemeasurement, the UE does not average the interference together withinterference in other sub-frames (e.g. sub-frame n used for uplinktransmission after another UL-DL reconfiguration in a next radio frame,sub-frames belonging to the same sub-frame set, or sub-frames belongingto the same CSI process). This is because the sub-frame in the exampledescribed above may be used for uplink transmission in the next radioframe. When another UL-DL reconfiguration is not performed in the nextradio frame (i.e., when the UL-DL configuration is maintained),interference can be processed together in sub-frame #n in the next radioframe. In the above description, “averaging” or “being processedtogether” implies inputting to one identical filter calculating thequantity of interference within a UE. A UE may include, in addition to afilter (or filters) for calculating the quantity of interference of atypical downlink sub-frame, a filter for calculating the quantity ofinterference in a sub-frame such as sub-frame #n when there is signalingfor another UL-DL reconfiguration.

In operation 814, the UE transmits channel information of sub-frame n ofa previous radio frame from the UE in sub-frame n of a radio framehaving a next index according to the method described above withreference to FIG. 7.

As a result of the determination in operation 811, if flexible sub-framen is used for uplink transmission without change, it is unnecessary toreceive downlink channel information for flexible sub-frame n from theeNB.

FIG. 9 is a block diagram illustrating an eNB apparatus in acommunication system according to an embodiment of the presentdisclosure.

Referring to FIG. 9, the eNB includes a transmission unit including aPDCCH block 905, a PDSCH block 916, a PHICH block 924, and a multiplexer915; a reception unit including a PUSCH block 930, a PUCCH block 939,and a demultiplexer 949; a controller 901, and a scheduler 903.

In the transmission unit, the PDCCH block 905 includes a DCI formatter907, a channel coder 909, a rate matching unit 911, and a modulator 913.The PDSCH block 916 includes a data buffer 917, a channel coder 919, arate matching unit 921, and a modulator 923. The PHICH block 924includes an HARQ ACK/NACK generator 925, a PHICH formatter 927, and amodulator 929.

In the reception unit, the PUCCH block 930 includes a demodulator 937, ade-rate matching unit 935, a channel decoder 933, and a data acquisitionunit 931. The PUCCH block includes a demodulator 947, a channel decoder943, and an uplink ACK/NAK or CQI acquisition unit 941.

The controller 901 refers to the quantity of available resources withinthe system and the like by using the channel information received fromthe UE according to the present disclosure and then notifies thescheduler 903 and the PDSCH block 916 of information.

In the PDCCH block 905, a DCI is configured under the control of thescheduler 903, an error correction capability is provided to the DCI,the DCI is rate-matched by the rate matching unit 911 in accordance withthe quantity of resources to be actually mapped, and the DCI ismultiplexed with other signals by the multiplexer 915.

In the PDSCH block 916, data to be transmitted is extracted from thedata buffer 917 under the control of the scheduler 903, the channelcoder 919 provides an error correction capability to the extracted data,the rate matching unit 921 rate-matches the data in accordance with thequantity of resources to be actually mapped, the modulator 923 modulatesthe rate-matched data, and the multiplexer 915 multiplexes the modulateddata with other signals.

In the PHICH block 924, under the control of the scheduler 903, the HARQACK/NACK generator 925 generates an HARQ ACK/NACK for a PUSCH receivedfrom the UE. The HARQ ACK/NACK is configured to accord with the PHICHstructure by the PHICH formatter 927, is modulated by the modulator 929,and is then multiplexed with other signals by the multiplexer 915.

An OFDM signal is generated from the multiplexed signals and is thentransmitted to the UE.

In the PUSCH block 730, the demultiplexer 949 separates a PUSCH signalfrom signals received from the UE, the demodulator 937 demodulates thePUSCH, the de-rate matching unit 935 reconfigures symbols before ratematching from the demodulated PUSCH signal, the channel decoder 933decodes the reconfigured symbols, and the data acquisition unit 931acquires PUSCH data from the decoded symbols. The data acquisition unit931 notifies the scheduler 903 whether a result of the decoding has anerror, to adjust the downlink HARQ ACK/NACK generation, and transfersthe information on whether the result of the decoding has an error tothe controller 901, so as to adjust the downlink HARQ ACK/NACKtransmission timing.

In the PUCCH block 939, the demultiplexer 949 separates a PUCCH signalfrom signals received from the UE. The demodulator 947 demodulates theseparated PUCCH signal, the channel decoder 943 decodes the demodulatedPUCCH signal, and the uplink ACK/NAK or CQI acquisition unit 941acquires an uplink ACK/NAK or CQI from the decoded PUCCH signal. Theacquired uplink CQI is provided to the scheduler 903 to be used indetermining a Modulation and Coding Scheme (MCS) for transmission of thePDSCH.

In a sub-frame operation device of a pico eNB, a controller reconfiguresa TDD UL-DL configuration or configures an uplink sub-frame as aflexible sub-frame.

The controller 901 uses a sub-frame, which is used for uplink datatransmission by a macro eNB, for downlink transmission. The controlleranalyzes channel information of the sub-frame received from a UE of apico eNB to use the analyzed channel information in scheduling downlinkdata in the sub-frame thereafter.

The controller 901 transmits reconfiguration information forreconfiguration of a TDD uplink/downlink to a UE and determines whetheran uplink HARQ process exists in a predetermined sub-frame changed froman uplink sub-frame to a downlink sub-frame by the reconfiguration. As aresult of the determination, when such an uplink HARQ process does notexist, the controller 901 transmits uplink data scheduling informationincluding a request for channel information to the UE in thepredetermined sub-frame or in a first sub-frame in which an uplink HARQprocess exists after the predetermined sub-frame. The controller 901controls to receive channel information transmitted from the UE in asub-frame at a predetermined timing.

The controller 901 may transmit reconfiguration information forreconfiguration of TDD uplink/downlink to a UE and transmit uplink datascheduling information including a request for channel information ofthe UE to the UE. The controller 901 may control to receive informationon interference measured only in a first sub-frame changed from anuplink sub-frame to a downlink sub-frame through the reconfigurationfrom the UE in an uplink sub-frame according to a predetermined timing.

The timing for receiving channel information from the UE has beendescribed above, so a detailed description thereof is omitted here.

FIG. 10 is a block diagram illustrating a UE apparatus in acommunication system according to an embodiment of the presentdisclosure.

Referring to FIG. 10, the UE includes a transmission unit including aPUCCH block 1005, a PUSCH block 1016, and a multiplexer 1015; areception unit including a PHICH block 1024, a PDSCH block 1030, a PDCCHblock 1039, and a demultiplexer 1049; and a controller 1001.

In the reception unit, the PUCCH block 1005 includes a UCI formatter1007, a channel coder 1009, and a modulator 1013. The PUSCH block 1016includes a data buffer 1018, a channel coder 1019, a rate matching unit1021, and a modulator 1023.

In the transmission unit, the PHICH block 1024 includes a HARQ ACK/NACKacquisition unit 1025 and a modulator 1029. The PDSCH block 1030includes a demodulator 1037, a de-rate matching unit 1035, a channeldecoder 1033, and a data acquisition unit 1031. The PDCCH block 1039includes a demodulator 1047, a de-rate matching unit 1045, a channeldecoder 1043, and a DCI acquisition unit 1041.

The controller 1001 determines whether a flexible sub-frame is used fordownlink transmission from a DCI received from an eNB and notifies thedetermined information to the PUCCH block 1005, the PUSCH block 1016,the PHICH block 1024, the PDSCH block 1030, and the PDCCH block 1039, soas to enable non-periodic channel information measurement. Thenon-periodic channel information measurement and transmission follow themethod as described above.

In the PUCCH block 1005, the UCI formatter 1007 configures an HARQACK/NACK or CQI according to the present disclosure by using UplinkControl Information (UCI) under a control of the controller 1001, thechannel coder 1009 provides an error correction capability to the HARQACK/NACK or CQI, the modulator 1013 modulates the HARQ ACK/NACK or CQIprovided with the error correction capability, and the multiplexer 1015multiplexes the modulated HARQ ACK/NACK or CQI with other signals.

In the PUSCH block 1016, data to be transmitted is extracted from thedata buffer 1018, the channel coder 1019 provides an error correctioncapability to the extracted data, the rate matching unit 1021rate-matches the data in accordance with the quantity of resources to beactually mapped, the modulator 1023 modulates the rate-matched data, andthe multiplexer 1015 multiplexes the modulated data with other signals.

A Single Carrier-Frequency Division Multiple Access (SC-FDMA) isgenerated from the multiplexed signals and is then transmitted to theeNB.

In the PHICH block 1024, the demultiplexer 1049 separates a PHICH signalfrom signals received from the UE, the demodulator 1029 demodulates theseparated PHICH signal, and the HARQ ACK/NACK acquisition unit 1025acquires a HARQ ACK/NACK for a PUSCH from the demodulated PHICH signal.

In the PDSCH block 1030, the demultiplexer 1049 separates a PDSCH signalfrom signals received from an eNB in a flexible sub-frame according tothe present disclosure, the demodulator 1037 demodulates the separatedPDSCH signal, the de-rate matching unit 1035 reconfigures symbols beforerate matching from the demodulated PDSCH signal, the channel decoder1033 decodes the reconfigured symbols, and the data acquisition unit1031 acquires PDSCH data from the decoded symbols. The data acquisitionunit 1031 notifies the PUCCH block 1005 of information on whether aresult of the decoding has an error, to adjust uplink HARQ ACK/NACKgeneration.

In the PDCCH block 1039, the demultiplexer 1049 separates a PDCCH signalfrom signals received from an eNB, the demodulator 1047 demodulates theseparated PDCCH signal, the channel decoder 1033 decodes the demodulatedPDCCH signal, and the DCI acquisition unit 1041 acquires DCI from thedecoded PDCCH signal.

In a UE of a pico eNB, the controller 1001 measures non-periodic channelinformation in order to use a sub-frame, which is used for uplinktransmission by a macro UE, for downlink transmission. The controllertransmits the non-periodic channel information in an uplink sub-frameaccording to the present disclosure.

The controller 1001 receives reconfiguration information forreconfiguration of a TDD uplink/downlink from an eNB and determineswhether an uplink HARQ process exists in a predetermined sub-framechanged from an uplink sub-frame to a downlink sub-frame by thereconfiguration. As a result of the determination, when such an uplinkHARQ process does not exist, the controller 1001 receives uplink datascheduling information including a request for channel information fromthe eNB in the predetermined sub-frame or in a first sub-frame in whichan uplink HARQ process exists after the predetermined sub-frame. Thecontroller 1001 controls to transmit channel information of the UE tothe eNB in a sub-frame at a predetermined timing.

The controller 1001 can receive reconfiguration information forreconfiguration of a TDD uplink/downlink from an eNB and measureinterference in the first sub-frame changed from an uplink sub-frame toa downlink sub-frame by the reconfiguration. The controller 1001 cancontrol to transmit information on the interference measured in only thefirst sub-frame to the eNB in an uplink sub-frame according to apredetermined timing.

The timing for transmitting channel information to the eNB by the UE hasbeen described above, so a detailed description thereof is omitted here.

At this point it should be noted that various embodiments of the presentdisclosure as described above typically involve the processing of inputdata and the generation of output data to some extent. This input dataprocessing and output data generation may be implemented in hardware orsoftware in combination with hardware. For example, specific electroniccomponents may be employed in a mobile device or similar or relatedcircuitry for implementing the functions associated with the variousembodiments of the present disclosure as described above. Alternatively,one or more processors operating in accordance with stored instructionsmay implement the functions associated with the various embodiments ofthe present disclosure as described above. If such is the case, it iswithin the scope of the present disclosure that such instructions may bestored on one or more non-transitory processor readable mediums.Examples of the processor readable mediums include Read-Only Memory(ROM), Random-Access Memory (RAM), CD-ROMs, magnetic tapes, floppydisks, and optical data storage devices. The processor readable mediumscan also be distributed over network coupled computer systems so thatthe instructions are stored and executed in a distributed fashion. Also,functional computer programs, instructions, and instruction segments foraccomplishing the present disclosure can be easily construed byprogrammers skilled in the art to which the present disclosure pertains.

While the present disclosure has been shown and described with referenceto various embodiments thereof, it will be understood by those skilledin the art that various changes in form and details may be made thereinwithout departing from the spirit and scope of the present disclosure asdefined by the appended claims and their equivalents.

What is claimed is:
 1. A method of transmitting channel information by a User Equipment (UE) in a communication system using a dynamic Time Division Duplex (TDD) UpLink-DownLink (UL-DL) configuration, the method comprising: receiving reconfiguration information for reconfiguration of TDD uplink and downlink from an evolved Node B (eNB); measuring, in response to the reconfiguration, interference in a first sub-frame changed from an uplink sub-frame to a downlink sub-frame by the reconfiguration; and transmitting information on interference measured in only the first sub-frame to the eNB in an uplink sub-frame according to a predetermined timing.
 2. The method of claim 1, wherein, in the measuring of the interference, measured interference to the first sub-frame is not averaged together with interference to other sub-frames except for the first sub-frame.
 3. The method of claim 1, further comprising, after receiving the reconfiguration information: determining whether an uplink HARQ process exists; receiving uplink data scheduling information requesting channel information from the eNB in the first sub-frame when the uplink HARQ process exists; determining whether the uplink data scheduling information includes a channel information request; and measuring interference to the first sub-frame when the uplink data scheduling information includes the channel information request.
 4. The method of claim 3, wherein the determining of whether the uplink data scheduling information includes a channel information request comprises determining whether to transmit the channel information according to whether a channel quality information request field included in the uplink data scheduling information is configured as ON.
 5. The method of claim 1, wherein the reconfiguration information is received through one of system information, higher layer signaling, Medium Access Control (MAC) signaling, and physical layer signaling.
 6. A method of receiving channel information by an evolved Node B (eNB) in a communication system using a dynamic Time Division Duplex (TDD) UpLink-DownLink (UL-DL) configuration, the method comprising: transmitting reconfiguration information for reconfiguration of TDD uplink and downlink to a User Equipment (UE); transmitting uplink data scheduling information including a request for channel information of the UE to the UE; and receiving information on interference measured in only a first sub-frame changed from an uplink sub-frame to a downlink sub-frame by the reconfiguration from the UE in an uplink sub-frame according to a predetermined timing, the measurement made in response to the reconfiguration.
 7. The method of claim 6, wherein the information on the interference measured in only the first sub-frame is not averaged together with interference to other sub-frames except for the first sub-frame.
 8. The method of claim 6, wherein the transmitting of the uplink data scheduling information comprises configuring a channel quality information request field included in the uplink data scheduling information as ON to request the channel information of the UE.
 9. The method of claim 6, wherein, the transmitting of the reconfiguration information comprises transmitting the reconfiguration information through one of system information, higher layer signaling, Medium Access Control (MAC) signaling, and physical layer signaling.
 10. A User Equipment (UE) transmitting channel information in a communication system using a dynamic Time Division Duplex (TDD) UpLink-DownLink (UL-DL) configuration, the UE comprising: a transmission/reception unit configured to transmit and receive a signal to and from an evolved Node B (eNB); and a controller configured to: receive reconfiguration information for reconfiguration of TDD uplink and downlink from the eNB, measure interference in a first sub-frame changed from an uplink sub-frame to a downlink sub-frame by the reconfiguration in response to the reconfiguration, and transmit information on interference measured in only the first sub-frame to the eNB in an uplink sub-frame according to a predetermined timing.
 11. The UE of claim 10, wherein the controller does not average measured interference to the first sub-frame together with interference to other sub-frames except for the first sub-frame.
 12. The UE of claim 10, wherein, after receiving the reconfiguration information, the controller controls to determine whether an uplink HARQ process exists, receive uplink data scheduling information requesting channel information from the eNB in the first sub-frame when the uplink HARQ process exists, to determine whether the uplink data scheduling information includes a channel information request, and to measure interference to the first sub-frame when the uplink data scheduling information includes the channel information request.
 13. The UE of claim 12, wherein the controller determines whether to transmit the channel information according to whether a channel quality information request field included in the uplink data scheduling information is configured as ON.
 14. The UE of claim 10, wherein the reconfiguration information is received through one of system information, higher layer signaling, Medium Access Control (MAC) signaling, and physical layer signaling.
 15. An evolved Node B (eNB) requesting channel information in a communication system using a dynamic Time Division Duplex (TDD) UpLink-DownLink (UL-DL) configuration, the eNB comprising: a transmission/reception unit configured to transmit and receive a signal to and from a User Equipment (UE); and a controller configured to: control to transmit reconfiguration information for reconfiguration of TDD uplink and downlink to the UE, transmit uplink data scheduling information including a request for channel information of the UE to the UE, and receive information on interference measured in only a first sub-frame changed from an uplink sub-frame to a downlink sub-frame by the reconfiguration from the UE in an uplink sub-frame according to a predetermined timing, the measurement made in response to the reconfiguration.
 16. The eNB of claim 15, wherein the information on the interference measured in only the first sub-frame is not averaged together with interference to other sub-frames except for the first sub-frame.
 17. The eNB of claim 15, wherein the controller configures a channel quality information request field included in the uplink data scheduling information as ON to request the channel information of the UE.
 18. The eNB of claim 15, wherein the controller transmits the reconfiguration information through one of system information, higher layer signaling, Medium Access Control (MAC) signaling, and physical layer signaling.
 19. A non-transitory computer-readable storage medium storing instructions that, when executed, cause at least one processor to perform the method of claim
 1. 20. A non-transitory computer-readable storage medium storing instructions that, when executed, cause at least one processor to perform the method of claim
 6. 